1. Field of the Invention
The invention relates to a medical or dental-medical handpiece.
2. Description of Related Technology
A handpiece is described for example in DE-AS 1 092 607. In the case of this known handpiece a holder device for a tool arranged in the forward end region of the handpiece has a drive sleeve which is arranged transversely to the longitudinal middle axis of the drive sleeve and is rotatably mounted in a rotary bearing having two roller bearings with a spacing from one another. The drive sleeve forms an insertion hole with a lateral insertion opening for the tool. On the side away from the insertion opening there is arranged a push button which can be pushed in against an elastic return force by means of finger pressure and thereby brings about a release of the tool. The push button has the cross-sectional form of a hat, with an outwardly outstanding flange at the lower edge of the hat shape, which flange engages behind an undercut in a screw part screwed into the handpiece and is thereby held on the handpiece in a manner such that it cannot be lost. The screw part serves on the one hand for an axial restriction of the rotary bearing and on the other hand the guiding and holding of the push button. With this known configuration there is present between the screw part and the handpiece a screw joint which runs out outwardly, which not only detracts from the appearance of the handpiece but in which also dirt and infection agents can collect. Further, for screwing in and screwing out of the screw part there is needed an engagement element on the screw part which is effective in a form-fitting manner, which is accessible from the outside and thus constitutes a further element in which dirt and infection agents can collect. Further the appearance of the handpiece is also diminished through such an engagement element.
In the case of a handpiece of modern construction, the screw part is formed with a flange lying upon the edge of the mounting opening, which serves the guiding and holding of a push button, which engages behind an undercut in the flange in the above-described manner. With this configuration there is likewise present between the flange in the handpiece a screw joint, whereby beyond this the flange bearing on the housing leads to an enlarged structure, which with regard to restricted treatment sites, in particular in the mouth of a patient, should be avoided.